RU2370935C1 - Method of using agricultural lands, polluted with heavy metals - Google Patents

Abstract

FIELD: agriculture.

SUBSTANCE: invention relates to field of agriculture and land recultivation. Method includes seeding of phytomeliorant plants, as such foddergrass mixtures containing not less than 60% of tetraploid rye-grass and polyploidy perennial cereals, such as timothy- grass and Bromus inermis. Norm of seeding is 20 - 24 kg/ha. High level of soil humidity up to 65-75% TMC and increased feeding mode are supported by carrying out fertilising watering. Herbage harvesting is performed at soil humidity not less than 65% TMC.

EFFECT: method allows to obtain feed production of high zootechnical quality, standard-pure as to content of heavy metals on polluted agricultural lands.

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Description

The present invention relates to the field of agriculture and may find application in the cultivation of crops on land containing heavy metals in quantities exceeding the maximum permissible concentration (MPC).

A known method of cleaning and reclamation of agricultural land contaminated with heavy metals, including the introduction into the contaminated soil layer of a sorption agent (montmorillonite) in an amount of 2 t / ha, followed by mixing (Pat. RF No. 2210438, MKI VC 1/00, BI No. 23, 2003).

This method requires significant costs for the acquisition and introduction of a sorption agent.

A known method of protecting soils from pollution by heavy metals, including sowing on these lands phytomeliorant plants that can carry and accumulate certain heavy metals in their aboveground biomass (US Pat. RF No. 2268096, MKI V09C 1/00, BI No. 02, 2006) .

This method is adopted as a prototype. Sowing plants-phytomeliorants allows for several years to reduce the content of heavy metals to the level of MPC. Mowed biomass can be used for disposal to recover heavy metals recovered from the soil.

The disadvantage of this method is the removal of land from agricultural use for the entire period of work on the extraction of contaminant metals from the soil. In addition, this method is effective only in the absence of renewable soil pollution. In most cases, the resumption of pollution is inevitable, since its source is existing industrial enterprises, transport, etc.

The aim of the invention is the use of agricultural land with an average degree of heavy metal pollution (up to 5 MPC) with obtaining a normatively clean agricultural products.

The goal is achieved by the method of using agricultural land contaminated with heavy metals, including planting phytomeliorant plants, in which, according to the invention, herbal mixtures containing at least 60% tetraploid varieties of ryegrass and polyploid perennial cereals, for example timothy grass meadow, beardless fire, are used when sowing rate of 20-24 kg / ha, while in the crops they maintain a high level of soil moisture up to 65-75% PV and an increased nutritional regime by fertilizing irrigation, and harvesting is carried out at a soil moisture of at least 65% PV.

The essence of the method lies in the fact that polyploid plants, especially in the composition of the grass mixture, have high viability in adverse soil and climatic conditions and, having a high buffer barrier, on soils contaminated with heavy metals are able to partially accumulate and fix polluting metals in the roots, taking them to the aerial part (green mass) only a small fraction of them. Of these, tetraploid ryegrass has the most powerful aerial part, so it should be at least 60% in the herbal mixture. The proposed method of using agricultural lands contaminated with heavy metals for growing polyploid plants allows to obtain large volumes of green mass for livestock feed with a content of heavy metals not exceeding the MPC on agricultural lands chronically contaminated with heavy metals.

The proposed method of using agricultural land contaminated with heavy metals is carried out in the following order.

On the site containing not more than 5 maximum concentration limits of zinc, copper and lead, pre-sowing treatment of the soil is carried out, including plowing with the introduction of the main fertilizer in the form of an organic-mineral mixture containing up to 50% of the calculated fertilizer norm, containing: N - 175-350, P - 90- 180, K - 225-450. The specific fertilizer application rate is specified taking into account the actual content of nutrients in the soil. A well-cultivated arable land is used for sowing a perennial herbal mixture, including seeds of polyploid varieties of timothy grass meadow, beechless bonfire and more than 60% tetraploid varieties of ryegrass. The seeding rate is 20-24 kg / ha with simultaneous row application of mineral fertilizers N - 20, P - 20, K - 20. The increased seeding rate allows for friendly seedlings and a dense grass stand with a well-developed root system. The root system provides absorption and fixation of polluting metals. At the same time, dense turf prevents the growth of weed vegetation, a high content of which in the biomass of the field can lead to an increase in the content of heavy metals in it.

After the emergence of seedlings in the crops control the moisture content of the arable layer of the soil. When it is reduced to 75% of the water supply, irrigation is carried out. Together with irrigation water, water-soluble forms of mineral fertilizers are applied. Maintaining a high level of soil moisture requires frequent watering, the combination of which with the application of fertilizers can increase the utilization rate of fertilizers due to their entry not only through the root system, but also through the leaf surface. Top dressing is stopped a week before harvesting or grazing animals of the aerial mass of plants.

It should be noted that tetraploid ryegrass has high requirements for providing moisture. With insufficient soil moisture, it sharply reduces productivity, which can lead to a significant increase in the content of heavy metal pollutants in the biomass. Therefore, in a contaminated area, soil moisture during the growing season should not fall below 75-65% of PV.

The root system of polyploid plants is capable of holding heavy metals absorbed from the soil in a bound state. Organic substances formed during the decomposition of the root mass of the grass mixture also bind the heavy metals contained in it, converting them into forms inaccessible to plants.

In the aerial part of ryegrass due to its large mass and high water cut, the content of heavy metals does not exceed the MPC value. When using the lands as hayfields, grass stands are harvested at 80% of the plants at the time of heading; during this period, grass stands has the highest biomass. In this case, one should not allow lowering the soil moisture below 65% of PV to avoid dusting during harvesting and contaminated soil getting onto the mown biomass.

It was experimentally established that in areas where the content of zinc, lead and copper is about 5 MAC in the plant mass of ryegrass tetraploid varieties grown by the proposed technology, their content in feed does not exceed the MPC. In this case, the metal content in the plant roots is hundreds of times higher than their content both in the aboveground mass and in the soil, which indicates the active accumulation and binding of these metals by the root mass of tetraploid ryegrass. The research results are presented in the table.

It should be noted that a certain excess of the content of zinc in the aboveground biomass of a plant can play a positive role, since zinc ions are cadmium antagonists and prevent its accumulation in plants.

The removal of heavy metals by plants of tetraploid ryegrass when their content in the soil is up to 5 MAC. Metals contained in the soil MPC (mg / kg) in the soil The metal content in the soil of the experiment (mg / kg) The metal content in the plant (mg / kg) In terrestrial biomass In the roots Zinc 55 300 50/72 * 50/3465 Copper 33 150 30 / 3.4 30/1264 Lead 32 150 5 / 0.9 5/219 Note *: MPC of metals in feed / metal content in biomass

Thus, the proposed method of using agricultural land contaminated with heavy metals allows growing mixtures of tetraploid ryegrass and other polyploid cereal grasses on lands with an average pollution level (up to 5 MAC) and using “chronically” contaminated agricultural land to obtain normatively clean heavy metals feed products of high zootechnical quality.

Claims (1)

A method of using agricultural land contaminated with heavy metals, including planting phytomeliorant plants on these lands, characterized in that grass mixtures containing at least 60% tetraploid ryegrass varieties and polyploid perennial cereals, for example, timothy grass meadow, beardless fire, are used as phytomeliorants sowing rate of 20-24 kg / ha, while in the crops they maintain a high level of soil moisture up to 65-75% of PV and an increased nutritional regime by means of fertilizer irrigation, and harvesting grass produce at a soil moisture content of at least 65% PV.